JP5771068B2 - High insulation film - Google Patents

Description

  The present invention relates to a highly insulating film.

  A film composed of a syndiotactic polystyrene resin composition (syndiotactic polystyrene film) is a film excellent in heat resistance, chemical resistance, hot water resistance, dielectric properties, electrical insulation, etc. Expected to be used. In particular, it is expected to be used as a capacitor insulator because of its excellent dielectric properties and high electrical insulation and heat resistance (Patent Documents 1 and 2). Further improvements have been made, for example, Patent Document 3 discloses a technique for improving the withstand voltage by suppressing impurities in the film, and Patent Document 4 provides handling and wear resistance by adjusting additive particles and the like. Patent Documents 5 and 6 disclose techniques for improving, as techniques for syndiotactic polystyrene films used for capacitor applications, respectively, for adjusting the refractive index of the film to improve thickness spots. Patent Document 7 discloses a technique for improving the dielectric breakdown voltage by adding an antioxidant.

  However, the syndiotactic polystyrene-based films disclosed in these Patent Documents 1 to 6 are used as an insulator of a capacitor. For example, the syndiotactic polystyrene film is higher than a capacitor mounted on a recent hybrid car. In a high performance capacitor, a film excellent in electrical characteristics such as dielectric breakdown voltage and heat resistance is required, and the performance may be insufficient. Further, the syndiotactic polystyrene film disclosed in Patent Document 7 is suitably used for a capacitor such as a hybrid car, but further improvement in heat resistance and dielectric breakdown voltage is required.

JP-A-1-182346 JP-A-1-316246 Japanese Patent Laid-Open No. 3-124750 Japanese Patent Laid-Open No. 6-80793 JP 7-156263 A JP-A-8-28396 JP 2009-235321 A

In view of the background art as described above, an object of the present invention is to provide a highly insulating film having excellent heat resistance and improved dielectric breakdown voltage.
Furthermore, in order to improve the capacitance of the capacitor or to reduce the size of the capacitor, it is required to further reduce the thickness of the film as an insulator. End up. Therefore, there is a demand for a film that is superior in handleability and that does not reduce the productivity in the film manufacturing process even if the film is thinned, and that can be adapted to the capacitor manufacturing speed that has been required in recent years.

  Therefore, the present invention provides a highly insulating film having further excellent electrical characteristics, a heat insulating property, a highly insulating film having excellent electrical characteristics even at high temperatures, winding property and workability. It is a desirable subject to obtain a highly insulating film excellent in handling properties such as.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have obtained a thermoplastic amorphous resin having a specific orientation structure and a high glass transition temperature Tg by DSC in a syndiotactic polystyrene biaxially stretched film. It has been found that heat resistance and breakdown voltage are improved by the inclusion, and the present invention has been achieved.

That is, the present invention employs the following configuration (1).
(1) A thermoplastic non-plastic film comprising a biaxially stretched film comprising a styrene polymer having a syndiotactic structure as a main component, and having a glass transition temperature Tg by DSC of 130 ° C. or higher with respect to the mass of the biaxially stretched film. The crystal resin Y contains 5% by weight to 48% by weight of polyphenylene ether and 0.1% by weight or more and 8% by weight or less of an antioxidant.
ΔP = (Nx + Ny) / 2−Nz (1)
(Where Nx is the minimum value of the refractive index in the plane direction of the film, Ny is the refractive index in the direction perpendicular to Nx in the plane direction of the film, and Nz is the refractive index in the thickness direction of the film. Show.)
A highly insulative film having a plane orientation coefficient (ΔP) of −0.027 or less is provided.

Moreover, this invention includes the following structures (2)-(7) as the preferable aspect.
(2) The highly insulating film according to the above (1) , wherein the refractive index in the thickness direction of the film is from 1.580 to 1.610 .
(3) The high value according to (1) above, wherein the absolute value of the difference between the minimum value (Nx) of the refractive index in the plane direction of the film and the refractive index (Nx) in the direction perpendicular to the direction is 0.025 or less. Insulating film.
(4) The highly insulating film according to the above (1), wherein the biaxially stretched film has a coating layer provided on at least one surface thereof and having a water contact angle of 85 ° or more and 120 ° or less.
(5) The above (4), wherein the coating layer contains at least one selected from the group consisting of a wax component, a silicone component, and a fluorine compound in an amount of 41% by mass to 94% by mass based on the mass of the coating layer. Highly insulating film according to the description.
(6) The highly insulating film according to any one of (1) to (5), wherein the thickness is 0.4 μm or more and less than 6.5 μm.
(7) The capacitor | condenser using the highly insulating film in any one of said (1)-(6).

According to the present invention, it is possible to provide a highly insulating film having excellent heat resistance and improved dielectric breakdown voltage.
Moreover, according to the preferable aspect of this invention, the highly insulating film excellent in the electrical property, heat resistance, and handleability can be provided. In particular, a highly insulating film having a high breakdown voltage can be obtained. Therefore, the highly insulating film obtained by the present invention can be suitably used as an insulator of a capacitor.

It is a figure which shows the sample and apparatus of heat resistance evaluation by this invention.

  The highly insulating film of the present invention is a biaxially stretched film whose main constituent is a styrene polymer described later, and contains a polymer Y having a glass transition temperature Tg by DSC of 130 ° C. or higher. The orientation structure is as follows. Furthermore, it is preferable to have a coating layer provided on at least one side of which the surface water contact angle is 85 ° or more and 120 ° or less. Here, “main” means that it exceeds 50% by mass, preferably 55% by mass or more, more preferably 60% by mass or more, and particularly preferably 65% by mass or more based on the mass of the biaxially stretched film. . If the ratio of the styrene polymer described below is less than the lower limit, film forming properties such as stretching are impaired. Moreover, it is preferable that the biaxially stretched film of this invention contains the inert fine particle and antioxidant which are mentioned later. Hereafter, each structural component which comprises the highly insulating film of this invention is demonstrated.

<Styrene polymer>
The styrenic polymer in the present invention is a styrenic polymer having a syndiotactic structure, that is, the side chain phenyl groups and substituted phenyl groups are alternately opposite to the main chain formed from carbon-carbon bonds. It has a three-dimensional structure located in the direction. In general, tacticity is quantified by nuclear magnetic resonance ( ¹³ C-NMR) with isotope carbon, and the abundance ratio of a plurality of consecutive constitutional units, for example, dyad in the case of two, triad in the case of three, In the case of five, it can be indicated by a pentad or the like. In the present invention, the syndiotactic styrenic polymer is 75% or more, preferably 85% or more, or 30% or more, preferably 50%, of racemic pentad (rrrr) in racemic diad (r). Polystyrene, poly (alkyl styrene), poly (halogenated styrene), poly (alkoxy styrene), poly (vinyl benzoate) having the above syndiotacticity, or a part of these benzene rings are hydrogenated A polymer, a mixture thereof, or a copolymer containing these structural units is designated. Here, as poly (alkylstyrene), poly (methylstyrene), poly (ethylstyrene), poly (propylstyrene), poly (butylstyrene), poly (phenylstyrene), poly (vinylnaphthalene), poly ( Vinyl styrene) and poly (acenaphthylene). Examples of poly (halogenated styrene) include poly (chlorostyrene), poly (bromostyrene), and poly (fluorostyrene). Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Among these, particularly preferable styrenic polymers include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (pt-butylstyrene), poly (p-chlorostyrene), and poly (p-chlorostyrene). (M-chlorostyrene), poly (p-fluorostyrene), and a copolymer of styrene and p-methylstyrene.

  Furthermore, in the case where a copolymer component is contained in a styrene polymer and used as a copolymer, the comonomer includes ethylene, propylene, butene, hexene, octene in addition to the styrene polymer monomer as described above. Olefin monomers such as butadiene, isoprene and other diene monomers, cyclic diene monomers and polar vinyl monomers such as methyl methacrylate, maleic anhydride and acrylonitrile.

The weight average molecular weight of the styrenic polymer is preferably 1.0 × 10 ⁴ or more and 3.0 × 10 ⁶ or less, more preferably 5.0 × 10 ⁴ or more and 1.5 × 10 ⁶ or less, particularly preferably at 1.1 × 10 ⁵ or more 8.0 × 10 ⁵ or less. By setting the weight average molecular weight to 1.0 × 10 ⁴ or more, a film having excellent strength characteristics and elongation characteristics and further improved heat resistance can be obtained. Moreover, when the weight average molecular weight is 3.0 × 10 ⁶ or less, the stretching tension is in a suitable range, and breakage or the like hardly occurs during film formation.

  A method for producing such a styrene polymer having a syndiotactic structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-187708. That is, in an inert hydrocarbon solvent or in the absence of a solvent, a styrene-based monomer (into the above-mentioned styrene-based polymer), using a titanium compound and a condensation product of water and an organoaluminum compound, particularly a trialkylaluminum, as a catalyst. It can be produced by polymerizing the corresponding monomer). Poly (halogenated alkylstyrene) is disclosed in JP-A-1-146912, and hydrogenated polymer is disclosed in JP-A-1-178505.

In the styrene polymer having a syndiotactic structure in the present invention, an appropriate amount of an additive such as a known antistatic agent can be blended if necessary. These blending amounts are preferably 10 parts by mass or less with respect to 100 parts by mass of the styrene polymer. If it exceeds 10 parts by mass, it tends to cause breakage during stretching, resulting in poor production stability.
Such a styrene polymer having a syndiotactic structure is remarkably superior in heat resistance as compared with a conventional styrene polymer having an atactic structure.

<Polymer Y>
In the highly insulating film of the present invention, the biaxially stretched film contains the following thermoplastic amorphous resin Y.
The thermoplastic amorphous resin Y in the present invention is a polymer having a glass transition temperature Tg determined by DSC (differential scanning calorimeter) of 130 ° C. or higher. In addition, the thermoplastic amorphous resin Y preferably has a Tg higher than the glass transition temperature of the styrene polymer. When such a thermoplastic amorphous resin Y is blended with the styrenic polymer, not only the glass transition temperature Tg as a mixture is increased, but also the heat resistance is improved, and the dielectric breakdown voltage at a high temperature is increased. In addition, the thermal dimensional stability of the highly insulating film is improved and the stretchability can be improved. From such a viewpoint, the glass transition temperature Tg of the thermoplastic amorphous resin Y is preferably 150 ° C. or higher, more preferably 180 ° C. or higher, and particularly preferably 200 ° C. or higher. The higher the glass transition temperature Tg of the thermoplastic amorphous resin Y to be blended, the greater the effect of improving the above effects such as thermal dimensional stability. Considering melt extrusion or the like, the substantial upper limit is preferably 350 ° C., more preferably 300 ° C.

Preferred examples of such thermoplastic amorphous resin Y include aromatic polyethers such as polyphenylene ether and polyetherimide represented by the following formula (1), polycarbonate, polyarylate, polysulfone, polyethersulfone, and polyimide. be able to. Of these, it is easy to improve the stretchability, and because there is a synergistic effect when combined with an antioxidant, not only the heat resistance and dimensional stability, but also the dielectric breakdown voltage is further improved. Polyphenylene ether represented by 1) is particularly preferred. Preferred examples of Q ₁ and Q ₂ in the following formula (1) include groups such as methyl, ethyl, and propyl. Specific examples of the polymer include poly-2,6-dimethyl-1,4-phenylene ether, poly-2,6-diethyl-1,4-phenylene ether, poly-2,6-dipropyl-1, 4-phenylene ether and the like. Among them, poly-2,6-dimethyl-1,4 obtained by copolymerizing poly 2,6-dimethyl-1.4-phenylene ether or 2,3,6-trimethylphenylene ether unit. -Phenylene ether is preferred. The method for producing polyphenylene ether is not particularly limited. For example, US Pat. Nos. 3,306.874, 3,306.875, 3.257.357, and 3. It can be produced by the reaction of phenols according to the procedure described in the specification of No. 257.358.

  The highly insulating film of the present invention comprises a resin composition in which a biaxially stretched film is blended in an amount of 5% by mass or more and 48% by mass or less of the above thermoplastic amorphous resin Y with respect to the mass of the biaxially stretched film. By blending the amount of the thermoplastic amorphous resin Y in the above range, the heat resistance is excellent and the effect of improving the dielectric breakdown voltage can be increased, that is, the dielectric breakdown voltage at a high temperature can be increased. When the content is too small, the heat resistance tends to be inferior, the effect of improving the dielectric breakdown voltage tends to be low, and the effect of improving the stretchability is poor. From such a viewpoint, the content of the thermoplastic amorphous resin Y is more preferably 8% by mass or more, further preferably 11% by mass or more, and particularly preferably 20% by mass or more. Moreover, when there is too much content, it exists in the tendency for the crystallinity of the styrene polymer of a syndiotactic structure to fall easily, and it exists in the tendency for the heat resistance of a film to be inferior. From such a viewpoint, the content of the thermoplastic amorphous resin Y is more preferably 45% by mass or less, further preferably 40% by mass or less, and particularly preferably 35% by mass or less.

<Antioxidant>
The highly insulating film of the present invention preferably contains the following antioxidant.
The antioxidant in the present invention may be either a primary antioxidant that captures the generated radicals to prevent oxidation or a secondary antioxidant that decomposes the generated peroxides to prevent oxidation. . Examples of the primary antioxidant include phenol-based antioxidants and amine-based antioxidants, and examples of the secondary antioxidant include phosphorus-based antioxidants and sulfur-based antioxidants.

  Specific examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, and 2-t-butyl-4-methoxy. Phenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4- [4,6-bis (octylthio) -1,3,5-triazin-2-ylamino] phenol, n And monophenol antioxidants such as octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6) -T-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl Hydrazine, N, N′-hexane-1,6-diylbis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide], 3,9-bis [1,1-dimethyl- Bispheno such as 2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane Le-based antioxidants. In addition, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t -Butyl-4-hydroxybenzyl) benzene, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], bis [3,3'-bis- (4'-hydroxy- 3'-t-butylphenyl) butyric acid] glycol ester, 1,3,5-tris (3 ', 5'-di-t-butyl-4'-hydroxybenzyl) -sec-triazine-2,4 High molecular type phenolic antioxidants such as 6- (1H, 3H, 5H) trione and d-α-tocophenol can be mentioned.

  Specific examples of amine-based antioxidants include alkyl-substituted diphenylamines.

  Specific examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenylditridecyl) phos. Phyto, octadecyl phosphite, tris (nonylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- (3,5-di- t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, Tris (2,4-di-t-butylphenyl Phosphite, cyclic neopentanetetrayl bis (2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetrayl bis (2,6-di-t-butyl-4-methylphenyl) phosphite 2,2′-methylenebis (4,6-di-t-butylphenyl) octyl phosphite and the like.

  Specific examples of the sulfur-based antioxidant include dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythritol. Examples include tetrakis (3-laurylthiopropionate) and 2-mercaptobenzimidazole.

  The antioxidant is particularly preferred from the viewpoint that it is more excellent in corrosion resistance and can further enhance the effect of improving the dielectric breakdown voltage, and among them, a primary antioxidant is preferable, and among them, a phenol-based antioxidant is particularly preferable.

  The antioxidant preferably has a thermal decomposition temperature of 250 ° C. or higher. When the thermal decomposition temperature is high, the effect of improving the dielectric breakdown voltage at a high temperature becomes high. If the thermal decomposition temperature is too low, the antioxidant itself is thermally decomposed at the time of melt extrusion, which tends to cause problems such as contamination of the process and yellowing of the polymer. From such a viewpoint, the thermal decomposition temperature of the antioxidant is more preferably 280 ° C. or higher, further preferably 300 ° C. or higher, and particularly preferably 320 ° C. or higher. The antioxidant in the present invention is preferably less susceptible to thermal decomposition and preferably has a higher thermal decomposition temperature, but in reality, the upper limit is about 500 ° C. or less.

  Moreover, it is preferable that melting | fusing point of antioxidant is 90 degreeC or more. If the melting point is too low, the antioxidant melts faster than the polymer during melt extrusion, and the polymer tends to slip at the screw supply portion of the extruder. As a result, the supply of the polymer becomes unstable, and problems such as the uneven thickness of the film occur. From such a viewpoint, the melting point of the antioxidant is more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 200 ° C. or higher. On the other hand, when the melting point of the antioxidant is too high, the antioxidant becomes difficult to melt during melt extrusion, and the dispersion in the polymer tends to be poor. Thereby, problems such as the effect of adding the antioxidant appear only locally. From such a viewpoint, the melting point of the antioxidant is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, further preferably 220 ° C. or lower, and particularly preferably 170 ° C. or lower.

  A commercial item can also be used as it is as the above antioxidant. Examples of commercially available products include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010), N, N′- Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine (manufactured by Ciba Specialty Chemicals: trade name IRGANOX1024), N, N′-hexane-1,6-diylbis [ 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionamide] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1098) is preferred.

  The content of the antioxidant is preferably 0.1% by mass or more and 8% by mass or less based on the mass of the biaxially stretched film. By containing the antioxidant in a content within the above numerical range, the effect of improving the dielectric breakdown voltage can be increased. When the content of the antioxidant is too small, the effect of adding the antioxidant is not sufficient, and the effect of improving the dielectric breakdown voltage tends to be low. From such a viewpoint, the content of the antioxidant is more preferably 0.2% by mass or more, further preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. On the other hand, when the content is too high, the antioxidant tends to aggregate in the biaxially stretched film, and the defects due to the antioxidant tend to increase. Less effective. From such a viewpoint, the content of the antioxidant is more preferably 7% by mass or less, further preferably 5% by mass or less, and particularly preferably 3% by mass or less.

  An antioxidant may be used individually by 1 type and may use 2 or more types together. When two or more types are used in combination, an embodiment using two or more types of primary antioxidants may be used, an embodiment using two or more types of secondary antioxidants may be used, or one or more types of primary antioxidants and 1 Two or more kinds of secondary antioxidants may be used in combination. For example, it can be expected to prevent both primary oxidation and secondary oxidation by using two types of antioxidants, a primary antioxidant and a secondary antioxidant, in combination. In the present invention, an embodiment in which a primary antioxidant is used alone or an embodiment in which two or more kinds of primary antioxidants are used is preferable from the viewpoint that the effect of improving the dielectric breakdown voltage can be further increased. An embodiment using a single antioxidant or an embodiment using two or more phenolic antioxidants is preferred.

  The highly insulating film of the present invention contains the above-described thermoplastic amorphous resin Y and antioxidant in a biaxially stretched film in the above-described manner, respectively. ) And heat resistance, that is, the dielectric breakdown voltage at high temperatures can be further increased.

  When the thermoplastic amorphous resin Y and the antioxidant are contained at the same time, the content ratio (the content of the thermoplastic amorphous resin Y / the content of the antioxidant) is 1 to 100. It is preferable. When the content ratio is in the above numerical range, the dielectric breakdown voltage and heat resistance are particularly excellent. If the content ratio is too small or too large, the effect of further increasing the electrical characteristics and heat resistance tends to be reduced. From such a viewpoint, the content ratio is more preferably 3 to 50, and particularly preferably 5 to 30.

<Inert fine particles>
The highly insulating film of the present invention has a biaxially stretched film containing inactive fine particles having an average particle size of 0.05 μm or more and 3.0 μm or less in a range of 0.05 to 3% by mass based on the mass of the biaxially stretched film. It is preferable to contain.

Specific inert fine particles are not particularly limited as long as they are stable with respect to syndiotactic polystyrene which is a matrix resin in a biaxially stretched film, and those known per se can be adopted. Specific inert fine particles include silicone resin particles, acrylic resin particles, styrene-acrylic resin particles, divinylbenzene-acrylic resin particles, polyester resin particles, polyimide resin particles, melamine resin particles, and other polymer resin particles (1 ) Silicon dioxide (including hydrates, silica sand, quartz, etc.); (2) Alumina in various crystalline forms; (3) Silicates containing 30% by mass or more of SiO ₂ component (eg amorphous or crystalline) Clay minerals, aluminosilicates (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc.); (4) oxides of Mg, Zn, Zr, and Ti; (5) Ca and Ba (6) Li, Ba, and Ca phosphates (including monohydrogen and dihydrogen salts); (7) Li, Na, and K benzoates; (8) Ca, Ba, Zn and Mn terephthalates; (9) Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, and Ni titanates; (10) Ba and Pb chromates (11) carbon (eg, carbon black, graphite, etc.); (12) glass (eg, glass powder, glass beads, etc.); (13) carbonates of Ca and Mg; (14) fluorite; (15) spinel type; Examples thereof include inorganic fine particles such as oxides.

Hereinafter, preferable inert fine particles will be described.
(Inert fine particles A)
In the highly insulating film of the present invention, the biaxially stretched film preferably contains inert fine particles A having an average particle diameter and a relative standard deviation of the particle diameter in a specific numerical range.
The average particle diameter of the inert fine particles A is 0.05 μm or more and 1.5 μm or less. By setting the average particle size of the inert fine particles A within the above numerical range, the film can have good air evacuation performance while maintaining a high dielectric breakdown voltage, and has high insulation properties with excellent winding properties. A film can be obtained, and an excellent processability can be obtained. When the average particle diameter of the inert fine particles A is too small, there is a tendency that sufficient air detachment properties cannot be obtained, the winding property is inferior, and the workability is also inferior. From such a viewpoint, the average particle diameter of the inert fine particles A is preferably 0.1 μm or more, more preferably 0.15 μm or more, and particularly preferably 0.2 μm or more. On the other hand, when the average particle size is too large, the size of voids in the film tends to increase, and the effect of improving the dielectric breakdown voltage is reduced. From such a viewpoint, the average particle diameter of the inert fine particles A is preferably 1.0 μm or less, more preferably 0.6 μm or less, and particularly preferably 0.5 μm or less.

  Further, the inert fine particles A have a relative standard deviation of the particle size of 0.5 or less. By setting the relative standard deviation of the particle size within the above numerical range, the height of the projection on the film surface becomes uniform, and the winding property is further improved. Moreover, coarse particles and coarse protrusions are reduced, and the effect of improving the dielectric breakdown voltage can be increased. From such a viewpoint, the relative standard deviation of the particle diameter of the inert fine particles A is preferably 0.4 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less.

  Furthermore, the inert fine particles A in the present invention are preferably spherical particles having a particle size ratio of 1.0 or more and 1.3 or less. The particle size ratio is more preferably 1.0 or more and 1.2 or less, and particularly preferably 1.0 or more and 1.1 or less. When the particle size ratio is in the above numerical range, the effect of improving the winding property and the effect of improving the dielectric breakdown voltage can be further increased.

  The content of the inert fine particles A is preferably 0.05% by mass or more and 2.0% by mass or less in 100% by mass of the biaxially stretched film. By containing the inert fine particles A in an amount in the above numerical range, it is possible to improve the handleability such as the film winding property while maintaining a high dielectric breakdown voltage, and to improve the workability. be able to. When the content of the inert fine particles A is too small, the air release property tends to be inferior and the winding property is inferior. From such a viewpoint, the content of the inert fine particles A is more preferably 0.1% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.1% by mass or more. On the other hand, when the content is too large, the film surface tends to become too rough, and thus the abrasion resistance of the film surface tends to deteriorate, and the effect of improving the dielectric breakdown voltage is lowered. In particular, in a capacitor application, the space factor tends to increase. From such a viewpoint, the content of the inert fine particles A is more preferably 1.0% by mass or less, further preferably 0.5% by mass or less, and particularly preferably 0.3% by mass or less.

  The inert fine particles A may be organic fine particles or inorganic fine particles, and those exemplified above are preferable. Among these organic fine particles, silicone resin particles and polystyrene resin particles are particularly preferable from the viewpoint of excellent slipperiness and abrasion resistance. Such polymer resin particles are preferably spherical as described above, that is, spherical polymer resin particles are preferred. Among these, spherical silicone resin particles and spherical polystyrene resin particles are particularly preferable from the viewpoint of superior slipperiness and abrasion resistance. Among the inorganic fine particles, calcium carbonate particles and silica particles are preferable, and silica particles are particularly preferable from the viewpoint of excellent slipperiness and abrasion resistance. Such inorganic fine particles are preferably spherical as described above, and spherical silica particles are particularly preferred from the viewpoint of superior slipperiness and abrasion resistance.

  Most preferable as the inert fine particles A are spherical silicone resin particles. When spherical silicone resin particles are used as the inert fine particles A, when polyphenylene ether is used as the polymer Y, the heat resistance is particularly high due to a synergistic effect.

<Inert fine particles B>
In the highly insulating film of the present invention, the biaxially stretched film may contain, in addition to the inert fine particles A, inert fine particles B having an average particle size and a relative standard deviation of the particle size in a specific numerical range. preferable.

  The average particle diameter of the inert fine particles B is 0.5 μm or more and 3.0 μm or less. By setting the average particle size of the inert fine particles B within the above numerical range, it is possible to obtain an appropriate slip property while maintaining a high dielectric breakdown voltage, and to enhance the effect of improving the winding property. When the average particle diameter of the inert fine particles B is too small, the slipping property tends to be low, and the effect of improving the winding property is low. From such a viewpoint, the average particle diameter of the inert fine particles B is preferably 0.7 μm or more, more preferably 1.0 μm or more, and particularly preferably 1.1 μm or more. On the other hand, if the average particle size is too large, the height of the protrusions on the film surface tends to be too high, thereby making the slipping property too high and causing end face deviation during winding, etc. Improvement effect is reduced. Furthermore, the wear resistance tends to deteriorate, and the effect of improving the dielectric breakdown voltage is reduced. From such a viewpoint, the average particle diameter of the inert fine particles B is preferably 2.0 μm or less, more preferably 1.5 μm or less, and particularly preferably 1.3 μm or less.

  The average particle diameter of the inert fine particles B is 0.2 μm or more larger than the average particle diameter of the inert fine particles A. By setting the difference between the average particle diameter of the inert fine particles A and the average particle diameter of the inert fine particles B as described above, high protrusions (protrusions having a relatively high height) due to the inert fine particles B on the film surface. Are scattered, and this makes air-removability between films better. At the same time, low protrusions due to the inert fine particles A are present, and the slipperiness between the films becomes better. With these, when winding the film into a roll shape, the balance between the air release property and the slipping property is good, and it is possible to obtain a film roll with a good winding shape even if it is wound at a high speed. The effect can be increased. From such a viewpoint, the average particle size of the inert fine particles B is preferably 0.4 μm or more larger than the average particle size of the inert fine particles A, more preferably 0.6 μm or more, and more preferably 0.8 μm or more. Embodiments are particularly preferred.

Further, the inert fine particle B has a relative standard deviation of the particle size of 0.5 or less from the same viewpoint as the above-mentioned inert fine particle A. The relative standard deviation of the particle diameter of the inert fine particles B is preferably 0.4 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less.
Further, the inert fine particles B are preferably spherical particles having a particle size ratio of 1.0 or more and 1.3 or less, more preferably 1.0 or more and 1. 2 or less, particularly preferably 1.0 or more and 1.1 or less.

  The highly insulating film of the present invention preferably contains the inert fine particles B as described above in an amount of 0.01% by mass to 1.5% by mass in 100% by mass of the biaxially stretched film. By containing the inert fine particles B in an amount in the above numerical range, it is possible to increase the effect of improving the handleability such as the winding property of the film while maintaining a high dielectric breakdown voltage. When the content of the inert fine particles B is too small, the slipping property tends to be low, and the effect of improving the winding property is low. From such a viewpoint, the content of the inert fine particles B is more preferably 0.05% by mass or more, further preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more. On the other hand, when there is too much content, the frequency of the void in a film tends to increase, and the improvement effect of a dielectric breakdown voltage becomes low. In addition, the slipping property tends to be too high, and the effect of improving the winding property is reduced, such as end face misalignment during winding. From such a viewpoint, the content of the inert fine particles B is more preferably 1.0% by mass or less, further preferably 0.5% by mass or less, and particularly preferably 0.4% by mass or less.

  As the inert fine particles B, the same organic fine particles and inorganic fine particles as the aforementioned inert fine particles A can be used. Among these, organic fine particles are preferable, and spherical silicone resin particles and spherical polystyrene resin particles are preferable, and spherical silicone resin particles are particularly preferable from the viewpoint of excellent slipperiness and abrasion resistance. Such organic fine particles are preferably spherical as described above, and spherical silicone resin particles are particularly preferred from the viewpoint of superior slipperiness and abrasion resistance. When spherical silicone resin particles are used as the inert fine particles B, when polyphenylene ether is used as the polymer Y, the heat resistance is particularly high due to a synergistic effect.

  As long as the inert fine particles A and the inert fine particles B used in the present invention are contained in the final biaxially stretched film, there is no limitation on the method of inclusion. For example, the method of adding in the arbitrary processes of melt extrusion is mentioned. Moreover, in order to disperse | distribute these microparticles | fine-particles effectively, a dispersing agent, surfactant, etc. can be used.

  In the present invention, when both the inert fine particles A and the inert fine particles B are used, a mode in which spherical silicone resin particles are respectively used can be preferably exemplified. In the particle size distribution curve, the above two types of particles show two particle size peaks that can be clearly distinguished, because the average particle size of each particle is different and the relative standard deviation of the particle size of each particle is small. That is, the inert fine particles A and the inert fine particles B can be clearly distinguished. In addition, when the two particle size peaks overlap each other at the base portion to form a valley portion, the particle size peak is decomposed into two particle size peaks with a point indicating a minimum value in the valley portion as a boundary.

<Inert particle C>
As described above, the highly insulating film of the present invention preferably contains inert fine particles A, and more preferably inert fine particles A and B. On the other hand, from the viewpoint of suppressing voids, it is an aggregate of primary particles instead of the inert fine particles A and B, the average particle diameter is 0.05 μm or more and 3 μm or less, and the pore volume is 0.05-2. It is also preferable to contain inert particles C that are 0 ml / g. Of course, the inert particles A and B may be used in combination. The average primary particle size of the inert particles C is preferably in the range of 0.01 to 0.1 μm. If the average particle size of the primary particles is less than 0.01 μm, ultrafine particles are generated by crushing at the slurry stage, which is not preferable because aggregates are formed. If the average particle size of the primary particles exceeds the upper limit, the porosity of the particles is lost, and as a result, the affinity with the polyester is lost and voids are easily generated. The pore volume is in the range of 0.05 to 2.0 ml / g, preferably 0.6 to 1.8 ml / g. If the pore volume is less than the lower limit, the porosity of the particles is lost, which is not preferable. On the other hand, if the pore volume is larger than the upper limit, crushing and aggregation tend to occur, and it is difficult to adjust the particle size. The average particle size (secondary particle size) of the inert fine particles C used in the present invention is preferably 0.05 μm or more and 3 μm or less, more preferably 0.7 to 2.7 μm, and particularly preferably 1.0 to 2.5 μm. . If the average particle size (secondary particle size) is less than the lower limit, the slipperiness of the film tends to be insufficient. On the other hand, if the average particle size (secondary particle size) exceeds the upper limit, the film surface becomes too rough, resulting in a capacitor. When the electrical characteristics are likely to deteriorate. The content of the inert particles C is 0.05 to 3% by weight, preferably 0.1 to 1% by weight, based on the mass of the biaxially stretched film. If the addition amount is less than the lower limit, the slipperiness of the film is insufficient. On the other hand, if the addition amount exceeds the upper limit, the surface of the film becomes too rough, and the electrical characteristics when used as a capacitor tend to deteriorate. Specific examples of the inert particles C include porous silica, alumina, and titanium oxide, and porous silica is particularly preferable.

<Other additives>
In the highly insulating film of the present invention, the biaxially stretched film is preferably composed of the styrenic polymer having the above-mentioned syndiotactic structure and the thermoplastic amorphous resin Y, and contains inert fine particles and an antioxidant. In order to further improve the moldability, mechanical properties, surface properties, etc., other resin components different from the thermoplastic amorphous resin Y can be contained.

  Examples of other resin components that can be contained include styrene polymers having an atactic structure, styrene polymers having an isotactic structure, styrene-maleic anhydride copolymers, and the like. A film that is easily compatible with the polymer, is effective in controlling crystallization when creating a preform for stretching, has improved stretchability, has easy control of stretching conditions, and has excellent mechanical properties. Preferred because it can be obtained. Among these, when a styrenic polymer having an atactic structure and / or an isotactic structure is contained, a styrene polymer having a syndiotactic structure is preferably used. The content ratio of these compatible resin components is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, with respect to 100 parts by mass of the syndiotactic styrene polymer. What should I do? When the content ratio of the compatible resin component exceeds 40 parts by mass, the effect of improving the heat resistance, which is an advantage of the styrenic polymer having a syndiotactic structure, is lowered.

Among the other resin components that can be contained, examples of resins that are incompatible with the styrenic polymer having a syndiotactic structure include polyolefins such as polyethylene, polypropylene, polybutene, and polypentene, polyethylene terephthalate, and polybutylene terephthalate. , Polyesters such as polyethylene naphthalate, polyamides such as nylon 6 and nylon 6,6, polythioethers such as polyphenylene sulfide, halogens such as polyacrylate, polysulfone, polyetheretherketone, polyethersulfone, polyimide, and Teflon (registered trademark) Resin other than the compatible resin, such as a vinyl fluoride polymer, an acrylic polymer such as polymethyl methacrylate, polyvinyl alcohol, and the like, and a cross-linked resin containing the compatible resin are also included. That. Since these resins are incompatible with the syndiotactic styrene polymer of the present invention, they can be dispersed in an island shape in the syndiotactic styrene polymer when contained in a small amount. It is effective for giving a moderate gloss after stretching or improving the slipperiness of the surface. The content ratio of the incompatible resin component is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less with respect to 100 parts by mass of the syndiotactic styrene polymer. . Moreover, when the temperature used as a product is high, it is preferable to contain a relatively heat-resistant incompatible resin component.
Furthermore, additives such as an antistatic agent, a colorant, and a weathering agent can be added within a range that does not impair the object of the present invention.

<Coating layer>
The highly insulating film of the present invention preferably has a coating layer having a water contact angle of 85 ° or more and 120 ° or less on at least one surface thereof. By having such a coating layer, the dielectric breakdown voltage can be increased. The reason for this is not clear, but it is considered that the presence of a thin coating layer between the biaxially stretched film and the electrode can alleviate charge concentration and improve the dielectric breakdown voltage. Further, when a coating layer that is a thin layer having a surface energy smaller than that of the biaxially stretched film is present, the coating layer is peeled off from the biaxially stretched film even when electric discharge occurs, and the biaxially stretched film that is a dielectric It is considered that the breakdown voltage is prevented and breakdown voltage is improved as a result. That is, in the present invention, when the water contact angle on the surface of the coating layer is in the above numerical range, the coating layer peels off from the film at the same time as voltage is applied and discharge occurs, and only the peeled coating layer is destroyed, It is considered that the breakdown voltage is improved as a result without being broken.

  For this reason, if the water contact angle of the coating layer is too low, the coating layer is difficult to peel off from the film even if a discharge occurs, and since the peeling is incomplete, the dielectric breakdown of the coating layer is induced and the dielectric breakdown of the film occurs. Therefore, the effect of improving the dielectric breakdown voltage by the coating layer cannot be obtained. Moreover, when the water contact angle of the coating layer is in the above range, it is possible to improve the slipping property and improve the winding property, and it is also possible to improve the heat resistance as seen by shear stress described later.

  From such a viewpoint, the water contact angle on the surface of the coating layer is preferably 86 ° or more, more preferably 88 ° or more, still more preferably 90 ° or more, and particularly preferably 95 ° or more. On the other hand, when the water contact angle is high, the coating layer tends to be peeled off from the film. Therefore, even when discharge occurs, only the easily peeled coating layer is broken, and the film is hardly broken down. However, if the water contact angle on the surface of the coating layer becomes too high, the adhesiveness with the metal layer formed on the capacitor becomes low, and particularly when the water contact angle exceeds 120 °, the adhesion with the metal layer is reduced. It tends to be inferior in performance and difficult to function as a capacitor. From such a viewpoint, the water contact angle on the surface of the coating layer needs to be 120 ° or less, preferably 115 ° or less, more preferably 110 ° or less, and further preferably 105 ° or less.

  In order to achieve the value of the surface water contact angle as described above, for example, a component that can reduce the surface energy after forming the coating layer, such as a wax component, a silicone component, or a fluorine component, is contained in the coating layer. Good. Moreover, the water contact angle in the coating layer surface can also be adjusted by adjusting these content and the thickness of a coating layer. Preferably, it is an embodiment in which the components described later are contained in the content described later. Of the wax component, silicone component, and fluorine component, the wax component and silicone component are particularly preferred.

  The type of the coating layer in the present invention is not particularly limited as long as the above-described surface water contact angle is achieved, but at least one selected from the group consisting of a wax component, a silicone component and a fluorine component is used as the mass of the coating layer. The content is preferably 41% by mass or more and 94% by mass or less. Here, the content indicates the total content of the wax component, the silicone component, and the fluorine component in the coating layer. When the coating layer contains at least one of these components in the above content, the surface energy of the coating layer can be easily made smaller than the surface energy of the film, and the water contact angle on the surface of the coating layer can be reduced. The numerical range can be achieved more easily. When the content is too small, the water contact angle tends to be difficult to increase. From such a viewpoint, the content of the above components is more preferably 51% by mass or more, and particularly preferably 65% by mass or more. On the other hand, if the content is large, the contact angle tends to increase, so that it tends to be preferable from the viewpoint of peeling of the coating layer, but if it is too much, it becomes difficult to form a uniform coating layer, for example, Defects in the coating layer such as missing coating are likely to occur, or the coating layer is easily peeled off from the film, and these improve the dielectric breakdown voltage improvement effect. In addition, when manufacturing a capacitor, the releasability of the coating layer is too high and the metal layer easily peels off, and the metal layer is easily detached during processing into a capacitor such as winding, resulting in a defective capacitor. May occur. From such a viewpoint, the content is more preferably 90% by mass or less, and particularly preferably 85% by mass or less.

(Wax component)
Examples of the wax component include synthetic waxes such as polyolefin waxes and ester waxes, and natural waxes such as carnauba wax, candelilla wax and rice wax. Examples of polyolefin waxes include polyethylene wax and polypropylene wax. Examples of ester waxes include ester waxes composed of aliphatic monocarboxylic acids having 8 or more carbon atoms and polyhydric alcohols, and specific examples thereof include sorbitan tristearate, pentaerythritol triplet. Nate, glycerin tripalmitate and polyoxyethylene distearate are exemplified. Among such waxes, it is preferable to use a polyolefin-based wax because the contact angle defined by the present invention is easily satisfied. Particularly preferred is polyethylene wax.
In addition, the wax is preferably water-soluble or water-dispersible from the viewpoint of exhibiting good dispersibility in the coating layer and thereby improving the dielectric breakdown voltage.

(Silicone component)
The silicone component is preferably a silicone composition mainly formed from a silicone compound having a reactive group. Here, “mainly” means, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more in the silicone component. By setting it as such an aspect, the improvement effect of a dielectric breakdown voltage can be made high. The silicone compound having no reactive group may be contained in the silicone component. However, if the content is too large (for example, 30% by mass or more in the silicone component), the formation of the vapor deposition layer is not possible. Difficult to evaluate as a capacitor. Therefore, the silicone compound having no reactive group is preferably 20% by mass or less, more preferably 10% by mass or less, in the silicone component.

  Examples of the silicone compound include polydimethylsiloxane in which a methyl group may be substituted with another alkyl group or a phenyl group. By using this, the effect of improving the breakdown voltage can be further increased. Can be high. Examples of the reactive group preferably include a hydrogen group, a vinyl group (including vinyl alkyl groups such as an allyl group), and a hydroxyl group. That is, as the silicone compound having a reactive group, polydimethylsiloxane having these reactive groups is particularly preferable. In the polydimethylsiloxane having such a reactive group, the reactive group has two or more reactive groups in the molecule and is usually directly bonded to a silicon atom. Then, due to heat applied at the time of forming the coating layer, preferably using a catalyst such as platinum or palladium, an addition reaction occurs in the hydrogen group and the vinyl group, or a condensation reaction occurs in the hydrogen group and the hydroxyl group, and curing is performed. Reaction occurs to form a crosslinked structure, resulting in a silicone composition.

The silicone compound may be a mixture of silicone compounds having different types of reactive groups. Such a silicone compound preferably has a molecular weight of 1,000 to 500,000. If it is less than 1000, the cohesive force of the coating film may be reduced and the coating layer may be easily lost. If it exceeds 500,000, the viscosity becomes high and handling may be difficult.
From the viewpoint of easy handling of the coating liquid for forming the coating layer and good dispersibility in the coating layer, thereby enhancing the effect of improving the dielectric breakdown voltage, the silicone compound and polydimethylsiloxane are water-soluble or It is preferably water-dispersible.

  In the present invention, the silicone compound is preferably used in combination with a silane coupling agent. Such a silane coupling agent is a silane compound having a hydrolyzable group directly bonded to a silicon atom, and preferably having a reactive group described later. The silane compound having a reactive group has a hydrolyzable group directly bonded to a silicon atom, and is selected from an organic group containing an amino group, an organic group containing an epoxy group, and an organic group containing a carboxylic acid group It is preferable to use one containing at least one group. The hydrolyzable group is an organic group that generates a silanol group by hydrolysis and reaction, such as an alkoxy group or a halogen group, such as a methoxy group or an ethoxy group.

  For example, specific examples of reactive groups in such silane compounds include organic groups containing amino groups such as primary amino groups such as 3-aminopropyl group, 3-amino-2-methyl-propyl group, and 2-aminoethyl group. Examples thereof include organic groups having primary and secondary amino groups, such as alkyl groups, N- (2-aminoethyl) -3-aminopropyl groups, and N- (2-aminoethyl) -2-aminoethyl groups. . Examples of the organic group containing an epoxy group include glycidoxyalkyl groups such as γ-glycidoxypropyl group, β-glycidoxyethyl group, γ-glycidoxy-β-methyl-propyl group, and 2-glycidoxycarbonyl-ethyl. And a glycidoxycarbonylalkyl group such as a 2-glycidoxycarbonyl-propyl group. Examples of organic groups that generate silanol groups by hydrolysis include alkoxy groups such as methoxy group, ethoxy group, butoxy group, and 2-ethylhexyloxy group, β-methoxyethoxy group, β-ethoxyethoxy group, and butoxy-β-ethoxy group. Such as alkoxy-β-ethoxy group, acetoxy group, propoxy group and the like, N-alkylamino group such as methylamino group, ethylamino group and butylamino group, N, N-dialkylamino group such as dimethylamino group and diethylamino group And heterocyclic groups containing nitrogen such as imidazole group and pyrrole group.

  Preferred silane coupling agents in the present invention include those having three methoxy groups as hydrolyzable groups, γ-glycidoxypropyl groups as reactive groups, and three ethoxy groups as hydrolyzable groups. Are bonded to form a reactive group and have a γ-glycidoxypropyl group. By adding such a silane coupling agent, the crosslinking density of the silicone compound thin film can be increased. When the coating film rigidity is increased, breakage of the film due to discharge can be further suppressed, and the dielectric breakdown characteristics are improved.

(Fluorine component)
Examples of the fluorine component include a polymer using a fluoroethylene monomer and a polymer using a fluorinated alkyl (meth) acrylate monomer. Examples of (co) polymers using fluoroethylene monomers include (co) polymers such as tetrafluoroethylene, trifluoroethylene, difluoroethylene, monofluoroethylene, and difluorodichloroethylene.

(Other additives)
In addition, the coating layer may contain a surfactant, a crosslinking agent, a lubricant and the like.
The surfactant is used for the purpose of increasing the wettability of the coating liquid for forming the coating layer on the film or improving the stability of the coating liquid. For example, polyoxyethylene-fatty acid ester, sorbitan fatty acid Examples include anionic and nonionic surfactants such as esters, glycerin fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, and alkyl sulfosuccinates. It is preferable that 1-60 mass% of surfactant is contained on the basis of the mass of an application layer.

  Moreover, the addition of a crosslinking agent is preferred because the cohesive force of the coating layer can be improved. Examples of the crosslinking agent include epoxy compounds, oxazoline compounds, melamine compounds, and isocyanate compounds, and other coupling agents can also be used. It is preferable that the addition amount of a crosslinking agent is 5-30 mass% on the basis of the mass of an application layer.

  Furthermore, the coating layer of the present invention is inert to the components forming the coating layer for the purpose of further improving the handleability of the resulting highly insulating film or preventing blocking between the films. Fine particles can be added. Such fine particles are preferably organic or inorganic inert fine particles, such as calcium carbonate, calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, silica particles, crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, crosslinked particles. Examples thereof include silicone resin particles.

  The thickness of the coating layer is preferably 0.005 to 0.5 μm, more preferably 0.005 to 0.2 μm, and still more preferably 0.02 to 0.1 μm as the thickness after drying. By setting the thickness of the coating layer within this range, when peeling and causing dielectric breakdown, energy of a larger voltage can be lost, and the effect of improving the dielectric breakdown voltage can be enhanced. When the thickness of the coating layer is less than the lower limit value, the effect of improving the dielectric breakdown voltage may not be sufficiently exhibited. Moreover, even if the thickness of the coating layer is increased to an extent that exceeds the upper limit value, a further effect of improving the dielectric breakdown voltage may not be obtained.

<Metal layer>
The highly insulating film of the present invention becomes a capacitor by, for example, laminating a metal layer on at least one side. The material of the metal layer is not particularly limited, and examples thereof include aluminum, zinc, nickel, chromium, tin, copper, and alloys thereof. Further, these metal layers may be slightly oxidized. Moreover, since a metal layer can be formed easily, it is preferable that a metal layer is a vapor deposition type metal layer formed by the vapor deposition method.

  Further, in laminating the metal layer, by further providing a metal layer on the surface of the coating layer of the present invention, the base material layer and the metal layer have an appropriate adhesive force, such as winding in film capacitor production. When processing is performed, the metal layer does not peel off, and the function as a capacitor is exhibited. Furthermore, at the same time, the coating layer and the metal layer have moderate adhesion, and even if a discharge occurs, the coating layer with a small surface energy is peeled off from the film first, and only the metal layer and the coating layer are destroyed. It is not destroyed, thereby not being short-circuited, and the effect of improving the dielectric breakdown voltage can be increased.

<Film characteristics>
(Plane orientation coefficient (ΔP))
In the highly insulating film of the present invention, the plane orientation coefficient (ΔP) based on the refractive index of the biaxially stretched film represented by the formula (1) is −0.027 or less. In the highly insulating film of the present invention, the more negative the plane orientation coefficient, the more the molecular chain is oriented in the film plane direction. Surprisingly, the plane orientation coefficient (ΔP) is below the upper limit. By making it, the heat resistance seen by the below-mentioned shear stress can be improved. From such a viewpoint, the upper limit of the plane orientation coefficient is preferably −0.029 or less, more preferably −0.030 or less, still more preferably −0.032 or less, and particularly preferably −0.033 or less.

  On the other hand, the lower limit of the plane orientation coefficient (ΔP) is not particularly limited, but the frequency of film breakage in the film production process, particularly in the stretching process tends to increase, and the productivity of the film tends to decrease. From such a viewpoint, the lower limit of the plane orientation coefficient (ΔP) is preferably −0.045 or more, more preferably −0.040 or more, further preferably −0.039 or more, and −0.038 or more. Particularly preferred.

  The plane orientation coefficient as described above is achieved by including the thermoplastic amorphous resin Y and adopting a manufacturing method as described later. That is, the preferred plane orientation coefficient in the present invention is such that the stretching ratio of the film is in a specific numerical range to be described later, and in the stretching step, the stretching in the direction perpendicular to the uniaxial direction is performed after the uniaxial stretching. This is achieved by dividing the stretching temperature into a plurality of stages and providing a specific temperature difference between the first stage temperature and the final stage temperature.

(Refractive index in the thickness direction)
In the highly insulating film of the present invention, the biaxially stretched film preferably has a refractive index in the thickness direction of from 1.580 to 1.635. By setting the refractive index in the thickness direction within the above numerical range, the dielectric breakdown voltage can be further increased. In addition, the frequency of film breakage in the film manufacturing process is reduced, and productivity is easily improved. From such a viewpoint, the refractive index in the thickness direction is preferably 1.620 or less, more preferably 1.615 or less, and particularly preferably 1.610 or less. On the other hand, when the refractive index in the thickness direction is too low, the dielectric breakdown voltage tends to be low.

  In the highly insulating film of the present invention, the frequency of film breakage in the capacitor production process increases, and the productivity of the capacitor tends to decrease. Furthermore, the thickness unevenness of the film tends to deteriorate, and it becomes difficult to obtain a capacitor with stable quality. From such a viewpoint, the refractive index in the thickness direction is preferably 1.590 or more, more preferably 1.595 or more, and particularly preferably 1.600 or more.

  The refractive index in the thickness direction as described above is achieved by incorporating the thermoplastic amorphous resin Y and employing a manufacturing method as described later. That is, the preferred refractive index in the thickness direction in the present invention is such that the stretching ratio of the film is in a specific numerical range to be described later, and in the stretching step, the film is stretched in the direction perpendicular to the uniaxial direction that is carried out after the uniaxial stretching. In the stretching, the stretching temperature is divided into a plurality of stages, and a specific temperature difference is set between the first stage temperature and the final stage temperature.

(Birefringence (ΔN))
The highly insulating film of the present invention has the absolute value (Δ) of the difference between the minimum refractive index (Nx) in the plane direction of the film and the refractive index (Ny) in the direction perpendicular to the direction indicating the refractive index of Nx. n) is preferably 0.025 or less. When ΔN is 0.25 or less, physical properties in the surface direction of the film are balanced, fine wrinkles due to shrinkage spots, deterioration of flatness, and the like can be suppressed, and heat resistance can be further improved on the lake. From these viewpoints, ΔN is more preferably 0.020 or less, further preferably 0.018 or less, and particularly preferably 0.015 or less.

(Film thickness)
The highly insulating film of the present invention preferably has a thickness of 0.4 μm or more and less than 6.5 μm. More preferably, it is 0.4 μm or more and less than 6.0 μm, and particularly preferably 0.5 μm or more and less than 3.5 μm. By setting the film thickness within the above numerical range, a capacitor having a high capacitance can be obtained.

  It is generally well known that a highly insulating film used as an insulator for a capacitor is preferably thinner because the capacitance of the capacitor is higher. However, when the film thickness is actually reduced (thinned), wrinkles are easily formed on the film, the film is easy to break, the handling property is lowered, and the added particles are easily dropped. Since problems such as lowering the breakdown voltage and lowering the absolute value of the dielectric breakdown voltage occur due to the thin film thickness, it is essential to balance them. In the present invention, the thermoplastic amorphous resin Y is included and the plane orientation coefficient is in a specific range so that the above-mentioned problem does not occur even if the film thickness is reduced. A highly insulating film having a novel structure provided with an agent, specific particles, and a specific coating layer is obtained by a manufacturing method described later.

(Film thickness unevenness)
The highly insulating film of the present invention preferably has a thickness unevenness of 10% or less, and can improve the electrical insulating effect. When thickness unevenness deteriorates, in-plane variation in electrical insulation tends to increase, and as a result, the effect of improving electrical insulation and dielectric breakdown voltage characteristics tends to decrease. From such a viewpoint, the thickness unevenness is preferably 9% or less, more preferably 6% or less, and further preferably 3% or less. The lower limit of the thickness unevenness is preferably as small as possible. Ideally, the thickness unevenness is 0%, but actually it is about 0.1% or more.
In order to make the thickness unevenness within the above numerical range, the stretching condition may be the mode described later. In particular, it is important that the transverse stretching conditions are divided into the above-described embodiments, that is, divided into a plurality of temperature regions.

  Moreover, in order to keep the thickness unevenness of a highly insulating film favorable, it can also mention preferably that the content in a biaxially stretched film does not deteriorate easily. This is because when the contents such as antioxidants and other additives are easily deteriorated at high temperatures or the weight is easily reduced, these deteriorated substances are deposited on the extrusion die lip during melt extrusion. This is because adhesion tends to occur, and the effect of this tends to cause streak irregularities on the film. Similarly, even when the content of contents such as antioxidants and other additives is too large, they tend to aggregate, tend to precipitate and adhere with an extrusion die lip, and tend to deteriorate thickness spots. is there. Therefore, in order to achieve the thickness spots, the thermal decomposition temperature and content of the antioxidant may be set within the range specified by the present invention.

(Dielectric breakdown voltage (BDV))
The highly insulating film of the present invention preferably has a dielectric breakdown voltage (BDV) at 120 ° C. of 350 V / μm or more. The fact that the dielectric breakdown voltage is in the above numerical range means that the dielectric breakdown voltage is excellent even at a high temperature. The breakdown voltage is more preferably 400 V / μm or more, and further preferably 420 V / μm or more. In order to achieve the dielectric breakdown voltage as described above, the specific coating layer described above is provided, and more preferably, the orientation of the biaxially stretched film, the thermoplastic amorphous resin Y in the film, and the antioxidant May be an embodiment that the present invention preferably defines. The dielectric breakdown voltage can also be adjusted by appropriately adjusting the mode of the inert fine particles. It is also effective to set the content ratio of the thermoplastic amorphous resin and the antioxidant (the content of the polymer Y / the content of the antioxidant) within the range that the present invention preferably defines. When the addition amount of the thermoplastic amorphous resin Y or the antioxidant is decreased, the dielectric breakdown voltage tends to be lowered. Further, when the content of inert fine particles is increased, the dielectric breakdown voltage tends to be lowered. Furthermore, by appropriately adjusting the contact angle of the surface of the coating layer in the present invention, the dielectric breakdown voltage can be improved and the above numerical range can be achieved.

  Further, the high insulation film of the present invention has a dielectric breakdown voltage at 23 ° C. of preferably 400 V / μm or more, more preferably 470 V / μm or more, and further preferably 510 V / μm or more. It can be achieved in a manner similar to voltage.

(Storage elastic modulus at 120 ° C. (E ′))
The highly insulating film of the present invention preferably has a storage elastic modulus (E ′) at 120 ° C. measured at a frequency of 10 Hz by dynamic viscoelasticity measurement of 600 MPa or more. When the storage elastic modulus (E ′) at 120 ° C. is in the above numerical range, the mechanical properties of the film under a high temperature environment are excellent. When the storage elastic modulus at 120 ° C. is too low, mechanical properties (breaking strength, breaking elongation, etc.) tend to decrease when used at high temperatures. From such a viewpoint, the storage elastic modulus at 120 ° C. is more preferably 650 MPa or more, further preferably 700 MPa or more, and particularly preferably 750 MPa or more. In order to achieve the storage elastic modulus (E ′) as described above, a thermoplastic amorphous resin Y is employed, and the aspect thereof is preferably defined by the present invention. When the content of the thermoplastic amorphous resin Y is decreased, the storage elastic modulus (E ′) tends to be lowered.

(Storage elastic modulus at 150 ° C. (E ′))
The highly insulating film of the present invention preferably has a storage elastic modulus (E ′) at 150 ° C. measured at a frequency of 10 Hz by dynamic viscoelasticity measurement of 370 MPa or more. It can be said that the higher the storage elastic modulus (E ′) at 150 ° C., the better the heat resistance. From these viewpoints, the storage elastic modulus (E ′) at 150 ° C. is more preferably 400 MPa or more, further preferably 430 MPa or more, and particularly preferably 460 MPa or more. In order to achieve the storage elastic modulus (E ′) at 150 ° C. as described above, the thermoplastic amorphous resin Y is employed, and the aspect is preferably defined by the present invention, and the draw ratio is increased. For example, it is effective to set the plane orientation coefficient within the above range. Note that when the content of the thermoplastic amorphous resin Y is decreased, the storage elastic modulus (E ′) tends to decrease.

(Loss elastic modulus (E ''))
In the highly insulating film of the present invention, the peak temperature of the loss elastic modulus (E ″) measured at a vibration frequency of 10 Hz by dynamic viscoelasticity measurement is preferably 120 ° C. or higher and 150 ° C. or lower. That the peak temperature of the loss modulus (E ″) is moderately high means that the temperature at which molecular motion begins to become active when the highly insulating film is heated is moderately high. Therefore, the heat resistance as a film tends to increase. From such a viewpoint, the peak temperature of the loss elastic modulus (E ″) is more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, and particularly preferably 135 ° C. or higher. On the other hand, the fact that the peak temperature of the loss elastic modulus (E ″) is too high has the combined effect that the molecular motion is less active, and the stretching stress during stretching becomes high. Sometimes breaks easily occur. From such a viewpoint, the peak temperature of the loss elastic modulus (E ″) is more preferably 145 ° C. or less, and further preferably 140 ° C. or less. In order to achieve the peak temperature of the loss elastic modulus (E ″) as described above, the thermoplastic amorphous resin Y may be employed and the content thereof may be adjusted as appropriate. More preferably, the content of the thermoplastic amorphous resin Y may be within the range that the present invention preferably defines. It is also effective to set the content ratio of the thermoplastic amorphous resin Y and the antioxidant (the content of the polymer Y / the content of the antioxidant) within the range preferably defined by the present invention. For example, when the content of the thermoplastic amorphous resin Y is increased, the peak temperature of the loss elastic modulus (E ″) tends to increase. If the content of the thermoplastic amorphous resin Y is too low, the peak temperature of the loss modulus (E ″) tends to be too low, and it tends to be difficult to reach 120 ° C.

(Dielectric loss tangent (tan δ))
The highly insulating film of the present invention preferably has a dielectric loss tangent (tan δ) at 120 ° C. and a frequency of 1 kHz of 0.0015 or less. When the dielectric loss tangent (tan δ) at 120 ° C. is large, when the film is used at a high temperature (for example, 120 ° C.) for a long time, it tends to self-heat and tends to be damaged. From such a viewpoint, the dielectric loss tangent (tan δ) at 120 ° C. is more preferably 0.0012 or less, further preferably 0.0009 or less, and particularly preferably 0.0006 or less. In order to achieve the dielectric loss tangent (tan δ) as described above, a thermoplastic amorphous resin Y may be employed and the content thereof may be appropriately adjusted. More preferably, the content of the polymer Y may be within a range that the present invention preferably defines. It is also effective to set the content ratio of the polymer Y and the antioxidant (the content of the polymer Y / the content of the antioxidant) within the range that the present invention preferably defines. For example, when the content of the polymer Y is reduced, the dielectric loss tangent (tan δ) tends to decrease.

(Heat shrinkage)
In the highly insulating film of the present invention, the average value of the heat shrinkage rate at 200 ° C. for 10 minutes in the longitudinal direction (machine axis direction) and the transverse direction (direction perpendicular to the machine axis direction and the thickness direction) is 6% or less. Preferably there is. When the thermal shrinkage is in the above numerical range, blocking that occurs during the processing of the capacitor (e.g., vapor deposition) can be suppressed, and a capacitor having excellent quality can be easily obtained. If the heat shrinkage rate is too large, blocking tends to occur during the processing of the capacitor (e.g., vapor deposition), and it tends to be difficult to obtain a good product. From such a viewpoint, the thermal shrinkage rate at 200 ° C. × 10 minutes is more preferably 8% or less, further preferably 4% or less, and particularly preferably 3% or less. In order to achieve the heat shrinkage rate as described above, the heat setting temperature may be in the range described below. When the heat setting temperature is increased, the heat shrinkage rate tends to decrease. Moreover, the numerical range of the said heat shrinkage rate can be achieved more effectively by performing a heat relaxation process at the time of heat setting or a subsequent process.

(Surface roughness)
In the highly insulating film of the present invention, the center line average surface roughness Ra of the surface of the coating layer on at least one side thereof is preferably 7 nm or more and 89 nm or less. By making the center line average surface roughness Ra within the above numerical range, the effect of improving the winding property can be enhanced. Moreover, blocking resistance improves and the external appearance of a roll can be made favorable. When the center line average surface roughness Ra is too low, the slipping property tends to be too low, and the effect of improving the winding property is lowered. From such a viewpoint, the center line average surface roughness Ra is preferably 11 nm or more, more preferably 21 nm or more, and particularly preferably 31 nm or more. On the other hand, when the center line average surface roughness Ra is too high, the slipping property tends to be too high, and the effect of improving the winding property, such as end face misalignment during winding, becomes low. From such a viewpoint, the centerline average surface roughness Ra is more preferably 79 nm or less, still more preferably 69 nm or less, and particularly preferably 59 nm or less.

In the highly insulating film of the present invention, the 10-point average roughness Rz of the surface of the coating layer on at least one side thereof is preferably 200 nm or more and 3000 nm or less. By setting the 10-point average roughness Rz within the above numerical range, the effect of improving the winding property can be increased. When the 10-point average roughness Rz is too low, the air release property tends to be low when the film is wound up as a roll, and the effect of improving the winding property such that the film is liable to slip is reduced. In particular, when the film thickness is thin, the film loses its elasticity, so that the air release property tends to be further lowered, and the effect of improving the winding property is further reduced. From such a viewpoint, the 10-point average roughness Rz is more preferably 600 nm or more, further preferably 1000 nm or more, and particularly preferably 1250 nm or more. On the other hand, when the 10-point average roughness Rz is too high, the number of coarse protrusions tends to increase, and the effect of improving the dielectric breakdown voltage is reduced. From such a viewpoint, the 10-point average roughness Rz is more preferably 2600 nm or less, further preferably 2250 nm or less, and particularly preferably 1950 nm or less.
Ra and Rz as described above can be achieved by employing inert fine particles defined by the present application.

<Film production method>
The high-insulating film of the present invention can be obtained by a method that has been conventionally known or accumulated in the industry, except for some special manufacturing methods. Hereinafter, the production method for obtaining the highly insulating film of the present invention will be described in detail.

  First, a resin composition in which a predetermined amount of inert fine particles, polymer Y, and antioxidant is blended with a syndiotactic styrenic polymer is heated and melted to prepare an unstretched sheet. Specifically, the resin composition is heated and melted at a temperature not lower than the melting point (Tm, unit: ° C.) and not higher than (Tm + 50 ° C.), extruded into a sheet, cooled and solidified to obtain an unstretched sheet. The intrinsic viscosity of the obtained unstretched sheet is preferably in the range of 0.35 to 0.9 dl / g. Next, this unstretched sheet is stretched biaxially. Stretching may be performed simultaneously in the machine direction (machine axis direction) and the transverse direction (direction perpendicular to the machine axis direction and the thickness direction) or sequentially in any order. For example, in the case of sequential stretching, first, in a uniaxial direction (glass transition temperature (Tg, unit: ° C.) − 10 ° C.) to (Tg + 70 ° C.) or less at a temperature of 3.2 times or more and 5.8 times or less, Preferably, the film is stretched at a magnification of 3.3 times to 5.4 times, more preferably 3.4 times to 5.0 times, and then a temperature of Tg or more (Tg + 80 ° C.) in a direction perpendicular to the uniaxial direction. 3.8 times to 5.9 times, preferably 4.0 times to 5.5 times, more preferably 4.1 times to 5.1 times, and even more preferably 4.2 times to 4.9 times. Stretch at a magnification of less than double. Furthermore, the area stretching ratio (= longitudinal stretching ratio × lateral stretching ratio) is preferably 12.0 times or more in order to obtain a film having the above-described plane orientation coefficient. If the area stretch ratio is low, the heat resistance becomes poor, which is not preferable. Therefore, the area stretch ratio is more preferably 13.0 times or more, further preferably 13.5 times or more, and particularly preferably 14.0 times or more. On the other hand, if the area stretch ratio is too high, breakage tends to occur during film formation and stretching, which is not desirable. From such a viewpoint, the area stretch ratio is preferably 22 times or less, more preferably 20 times or less, still more preferably 18 times or less, and particularly preferably 17 times or less.

In the present invention, as described later, an unstretched sheet, such an unstretched sheet, preferably a uniaxially stretched film uniaxially stretched in the longitudinal direction, by applying a coating liquid for forming a coating layer, It is preferable to form a coating layer.
In the stretching in the direction perpendicular to the uniaxial direction, the crystallization is progressed in the previous stretching, so that the stretching becomes difficult and the film is easily broken during film formation. In particular, when a thin film having a film thickness of about 3 μm is formed, and particularly in a region where the draw ratio is 4.0 times or more, breakage easily occurs.

  As a result of examining this measure, it has been found that it is effective to set the stretching speed within a specific numerical range in stretching in the direction perpendicular to the uniaxial direction. That is, if the stretching speed is too high, the higher-order structure change of the molecule due to stretching cannot follow the speed of the shape change of the film due to stretching, and the higher-order structure is likely to be distorted. It tends to occur. From such a viewpoint, the stretching speed is preferably 30000% / min or less, more preferably 15000% / min or less, further preferably 9000% / min or less, and particularly preferably 6000% / min or less. On the other hand, if the stretching speed is too slow, crystallization of the film precedes in the middle of stretching, and variation in stretching stress is likely to occur, and stretch spots and thickness spots are likely to occur, thereby causing breakage. From such a viewpoint, the stretching speed is preferably 500% / min or more, more preferably 1000% / min or more, further preferably 2000% / min or more, and particularly preferably 4000% / min or more.

  Further, as another effective means for suppressing breakage, in the stretching in the direction perpendicular to the uniaxial direction, the stretching temperature is not made constant, but is divided into a plurality of stages. It has been found that it is effective to make a temperature difference between the step temperatures. The temperature difference is preferably 4 ° C. or higher, more preferably 7 ° C. or higher, more preferably 12 ° C. or higher, particularly preferably 15 ° C. or higher. . Moreover, when the temperature difference is too large, film breakage tends to occur. Moreover, it exists in the tendency for the uneven thickness of the film after extending | stretching to worsen. From such a viewpoint, the temperature difference is preferably 49 ° C. or less, more preferably 39 ° C. or less, further preferably 29 ° C. or less, and particularly preferably 20 ° C. or less. In this way, by setting the temperature difference between the first stage and the final stage within the above numerical range, and further by setting it to three or more stages, a high draw ratio that has been difficult in the past in the production of a thin film is obtained. That is, a high refractive index in the thickness direction and a low plane orientation coefficient can be achieved. Moreover, a film with favorable thickness spots can be obtained thereby.

  In the process of performing stretching in the direction perpendicular to the uniaxial direction, in order to set a temperature difference between the first stage and the final stage, the zone inlet (first stage) and outlet (final stage) in one stretching zone The temperature difference may be given by or two or more continuous drawing zones having different temperatures may be provided, and the temperature difference may be given by the first drawing zone (first stage) and the last drawing zone (final stage). Good. Here, the zone indicates one area divided by a shutter or the like in a tenter or the like. In any case, it is preferable to further divide between the first stage and the final stage, and to increase the temperature in a gradient from the first stage toward the final stage. For example, when two or more continuous stretching zones having different temperatures are used, it is preferable to further provide one or more stretching zones between the first stretching zone and the last stretching zone, and to provide 12 to 10 stretching zones. More preferably. Setting the total number of stretching zones to 11 or more is disadvantageous from the viewpoint of equipment costs. For example, when the film is stretched in the width direction, a value obtained by dividing the film width immediately after leaving the final stage by the film width immediately before entering the first stage may be a target draw ratio. It is preferable to increase the film width in an inclined manner, and it is particularly preferable to increase the film width linearly. In the case where the machine direction and the transverse direction are drawn simultaneously, the drawing temperature is similarly divided into a plurality of stages, and a temperature difference is provided between the first stage temperature and the final stage temperature.

  In the present invention, these means can be preferably exemplified as means for achieving the preferred refractive index and in the thickness direction in the present invention. Furthermore, when these means are employed, breakage is unlikely to occur even if the film thickness is reduced, and therefore these means can be exemplified as preferred means for achieving the preferred film thickness in the present invention. In the present invention, it is preferable to employ at least one of the above-described stretching speed mode and stretching temperature mode, but it is more preferable to employ both modes, and the stretching process is stable. It becomes easy to achieve the preferable refractive index and preferable film thickness in the present invention.

  Next, heat setting is performed at a temperature of (Tg + 70 ° C.) to Tm. The heat setting temperature is 200 ° C. or higher and 260 ° C. or lower, preferably 225 ° C. or higher and 255 ° C. or lower, and more preferably 235 ° C. or higher and 250 ° C. or lower. When the heat setting temperature is too high, film breakage is likely to occur particularly when a film having a thin film thickness is produced, and the thickness unevenness is deteriorated. If the relaxation treatment is performed at a temperature lower by 20 ° C. to 90 ° C. than the heat setting temperature as necessary after the heat setting, the dimensional stability is improved.

<Coating and drying of coating layer>
In the present invention, the coating layer is a coating solution for forming a coating layer obtained by blending each component constituting the coating layer described above, applied to the surface on which the coating layer is to be formed in the film, and dried. Cure and form as needed. In addition, this coating liquid can be diluted using a suitable solvent, and a density | concentration and a viscosity can be adjusted. As such a solvent, water is preferably used from the viewpoint of ease of handling, and thus each component is preferably water-soluble or water-dispersible.

  The coating layer may be formed by a so-called in-line method formed during film production or a so-called off-line method formed after film production. From the viewpoint of productivity and the viewpoint that a stronger coating layer can be obtained, it is preferable to employ an in-line method. In the in-line method, in the film production process, it may be applied to an unstretched sheet, may be applied to a uniaxially stretched film uniaxially stretched in the longitudinal or lateral direction, or may be applied biaxially stretched in the longitudinal and lateral directions. It may be applied to an axially stretched film (including those that have undergone orientation crystallization and those that have not been completed), but from the viewpoint of adhesion between the film and the coating layer, it is applied to an unstretched sheet or a uniaxially stretched film. It is preferable to do.

  Specifically, in the case of simultaneous biaxial stretching, it is preferable to apply a coating solution to an unstretched sheet before stretching. In the case of sequential biaxial stretching, the coating liquid may be applied in a stage before stretching in the first axial direction, or after stretching in the first axial direction and in the second axial direction. You may apply | coat a coating liquid in the step before performing. Among these, it is easy to suppress the occurrence of scratches by applying the coating liquid in the stage after stretching in the first axial direction and before stretching in the second axial direction. It is preferable because there is a heat treatment fixing that advances the process, and the structure of the coating layer is easily stabilized.

  Moreover, it is preferable that the coating film obtained by apply | coating a coating liquid is dried to some extent until it enters into the following process. For example, when stretching is performed after coating, if the coating film is not sufficiently dried, temperature fluctuations are likely to occur in the film during stretching, and unevenness occurs in the stretching, resulting in poor film thickness irregularities.

  The coating film may be dried independently after application of the coating liquid, or may be performed continuously from the coating process by providing a drying process before the stretching process, and a preheating process in the stretching process may be applied. You may divert as a drying process of a film | membrane. The lower limit of the drying temperature is 60 ° C or higher, preferably 70 ° C or higher, more preferably 80 ° C or higher. The upper limit is preferably 125 ° C or lower, more preferably 115 ° C or lower, further preferably 105 ° C or lower, and the drying time is 0.1 minutes or more and 10 minutes or less are preferable. If the drying temperature is too high or the drying time is too long, the crystallization of the film will proceed before stretching, the stretching stress will increase and the stretchability will decrease, and there will be many breaks during stretching. If the drying temperature is too low or the drying time is too short, the coating liquid tends to be insufficiently dried, and the diluting solvent remains in the coating film even in the stretching process. However, the evaporation occurs, stretch spots tend to occur, and the film thickness spots tend to deteriorate.

  Further examination of these reveals that the drying temperature is more strongly dependent on the drying time, and as a result, the value of [drying temperature (° C.) × drying temperature (° C.) × drying time (minutes)] is obtained. It is preferably 1000 or more, more preferably 3000 or more, further preferably 8000 or more, preferably 100,000 or less, more preferably 70,000 or less, and more preferably 30,000 or less. It turned out to be even better.

  Here, the drying temperature is expressed as an average of the first temperature and the last temperature in the drying process when the coating film drying process exists apart from the stretching process. In the case where there is a drying process in succession to the application of the coating, it is expressed as an average of the initial temperature of the drying process and the temperature of the last part of the drying process (the initial temperature of the stretching process). The preheating part before a extending process may become a drying process.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. Various characteristic values in the examples were measured and evaluated by the following methods.

(1) Average particle size and particle size ratio of the particles The powder is dispersed on the sample stage so that the individual particles do not overlap as much as possible, and a gold thin film deposited layer is formed on the surface with a thickness of 200 to 300 mm by a gold sputtering device. Formed. Next, observation was performed at 10,000 to 30,000 times using a scanning electron microscope, and the area equivalent particle diameter (Di), major axis (Dli) and at least 1000 particles were measured with a Luzex 500 manufactured by Japan Regulator Co., Ltd. The short diameter (Dsi) was determined.

In addition, the relative standard deviation of the powder was obtained from the following equation from the obtained area equivalent particle diameter (Di) and average particle diameter (D) of each particle.

(2) Film surface roughness (Ra)
Measurement length (Lx) 1 mm, sampling pitch 2 μm, cut-off using a non-contact type three-dimensional roughness meter (Kosaka Laboratories, ET-30HK) with a semiconductor laser with a wavelength of 780 nm and an optical stylus with a beam diameter of 1.6 μm Under the conditions of 0.25 mm, thickness direction enlargement magnification of 10,000 times, lateral direction enlargement magnification of 200 times, and the number of scanning lines of 100 (therefore, the Y-direction measurement length Ly = 0.2 mm), Measure the protrusion profile on the surface. When the roughness curved surface was represented by Z = f (x, y), the value obtained by the following formula was defined as the center line average surface roughness (Ra, unit: nm) of the film.

(3) Thermal contraction rate The thermal contraction rate (longitudinal direction and lateral direction) (unit:%) of the film in 10 minutes in an atmosphere of 200 ° C. in a no-tension state was determined, and the average thereof was taken as the average thermal contraction rate.

(4) Refractive index Using the Abbe refractometer using sodium D line (589 nm) as a light source, the minimum refractive index direction is obtained in the plane direction at 23 ° C. and 65% RH, and the refractive index is defined as (Nx). The refractive index in the direction perpendicular thereto was defined as (Ny), and the refractive index (Nz) in the thickness direction was further measured. And the plane orientation coefficient ((DELTA) P) was calculated | required by the following formula.
ΔP = (Nx + Ny) / 2−Nz
Further, birefringence (ΔN) was measured by the following formula.
ΔN = Nx−Ny

(5) Dielectric breakdown voltage (BDV)
It measured according to the plate electrode method shown by JIS C 2151. Using a DC withstand voltage tester in an atmosphere of 23 ° C. and 50% relative humidity, the upper electrode is a brass cylinder with a diameter of 25 mm, the lower electrode is an aluminum cylinder with a diameter of 75 mm, and the pressure is increased at a pressure increase rate of 100 V / second. The voltage (unit: V) when the film was broken and short-circuited was read. The obtained voltage was divided by the film thickness (unit: μm) to obtain a dielectric breakdown voltage (unit: V / μm). The measurement was performed at 41 points, and the median value of the remaining 21 points was taken as the measured value of the dielectric breakdown voltage except for the larger 10 points and the smaller 10 points.
For measurement at 120 ° C., electrodes and samples were set in a hot-air oven, connected to a power source with a heat-resistant cord, and pressure increase was started 1 minute after the oven was put in.

(6) Stretchability Judgment was made as follows based on the number of breaks that occurred while a biaxially stretched film was formed to 50,000 m.
Stretchability ◎: Less than 1 break per 50,000 m film formation Stretchability ○: 1 to less than 2 breaks per 50,000 m film formation Stretchability Δ: Break per 50,000 m film formation 2 times to less than 4 times Stretchability x: per 50,000 m of film formation, breakage 4 times to less than 8 times Stretchability xx: Per breakage of 50,000 m film formation, 8 times or more

(7) Rewindability In the film manufacturing process, the film was wound up into a roll of 500 mm width and 7000 m at a speed of 160 m / min, and the roll shape obtained and the end face deviation at the end face of the roll were rated as follows. did.
[Rolling appearance]
A: There are no pimples on the surface of the roll, and the winding shape is good.
B: There are 1 to 4 pimples (protruding bulges) on the surface of the roll, and the winding shape is almost good.
C: There are 4 or more and less than 10 pimples (protruding bulges) on the surface of the roll, and the wound form is somewhat poor, but it can be used as a product.
D: There are 10 or more pimples (protruding protrusions) on the surface of the roll, the winding shape is poor, and it cannot be used as a product.
[Edge misalignment]
(Double-circle): The end surface shift | offset | difference in a roll end surface is less than 0.5 mm, and is favorable.
○: The end face deviation at the end face of the roll is 0.5 mm or more and less than 1 mm, which is almost good.
(Triangle | delta): The end surface shift | offset | difference in a roll end surface is 1 mm or more and less than 2 mm, and although it is a little inferior, it can be used as a product.
X: The end face deviation at the end face of the roll is 2 mm or more, which is inferior and cannot be used as a product.
XX: The end face shift increases during roll winding, and a 7000 m roll cannot be created.

(8) Pyrolysis temperature Using a differential thermothermal gravimetric simultaneous measurement device (Seiko Denshi Kogyo Co., Ltd .: trade name TG / DTA220), the temperature is measured at a temperature increase rate of 10 ° C./min in an air atmosphere. / The temperature at which the weight starts to change from the weight change curve was determined by the tangential method and was defined as the thermal decomposition temperature (unit: ° C).

(9) Glass transition temperature and melting point About 20 mg of a sample was sealed in an aluminum pan for measurement, and mounted on a differential scanning calorimeter (DSC) (manufactured by TA Instruments: trade name DSCQ100, from room temperature (25 ° C.) to 20 ° C. The sample was heated up to 280 ° C. at a rate of / min and the melting point was measured. Thereafter, the sample was rapidly cooled and then heated again at a rate of 20 ° C./min and the glass transition temperature (unit: ° C.) was measured.

(10) Storage elastic modulus (E ′), loss elastic modulus (E ″), dielectric loss tangent (tan δ)
Using a dynamic viscoelasticity measuring device (Orientec Co., Ltd., DDV-01FP), the storage elastic modulus of the film sample (at a vibration frequency of 10 Hz while raising the temperature from 25 ° C. to 230 ° C. at a rate of 2 ° C./min. E ′) (unit: MPa) and loss elastic modulus (E ″) (unit: MPa) were measured. At this time, the sample length was 4 cm in the measurement direction × 3 mm in the width direction (3 cm between chucks). From the above measurement results, the peak temperature (unit: ° C.) of the loss elastic modulus (E ″), the storage elastic modulus at a temperature of 120 ° C., the storage elastic modulus (E ′) at a temperature of 150 ° C. (unit: MPa). Asked. In addition, it measured about each of the vertical direction and the horizontal direction of a film, and calculated | required and calculated | required those average values.
In addition, the dielectric loss tangent (tan δ) was obtained by measurement under the conditions of a temperature of 120 ° C. and a vibration frequency of 1 kHz using a dielectric loss measuring machine (TR-10C) manufactured by Ando Electric. The sample was prepared by aluminum vapor deposition according to JIS C 2151. In addition, it measured about each of the vertical direction and the horizontal direction of a film, and calculated | required and calculated | required those average values.

(11) Heat resistance (shearing force after thermocompression bonding)
The shear force was measured with the apparatus shown in FIG. The upper drawing of FIG. 1 is a view when the sample and the apparatus are viewed from the horizontal direction, and the lower view is a view when the sample and the apparatus are viewed from the upper side in the vertical direction.
1 and 2 in FIG. 1 are evaluation samples 1 and 2 cut in a film forming direction of 50 mm and a width direction of 200 mm, and 3 is a 50 mm × 50 mm square hot plate placed horizontally, as shown in FIG. Sample 1 and sample 2 were installed. At this time, when the samples 1 and 2 have the coating layer only on one side, the coating layer and the hot plate are installed so that they do not contact each other, and the sample 2 to be installed has a surface different from the sample 1 attached thereto. Was installed. Further, a smooth paper 4 was placed thereon. Then, a temperature of 125 ° C. was applied to the lower hot plate, the terminal 5 having a crimping area of 6.16 square cm (φ28 mm) was lowered from the upper portion in the vertical direction, and the sample was thermocompression bonded at a pressure of 1 MPa for 60 seconds.
Then, the both ends of the film forming direction of the thermocompression-bonded film were gripped and pulled using a load cell, and the maximum load at which the thermocompression-bonded portion was broken was measured. The measurement was carried out five times, and the three values in the center except the maximum and minimum values were averaged, and this was used as the shear force (g). It can be said that the smaller the shear force, the better the heat resistance.

(12) Water contact angle On the surface of the coating layer of the film, measurement was performed 5 times using a Kyowa Interface Science contact angle meter (model: CA-A), and the water contact angle (°) with the average value. It was.
In addition, the measurement is performed by slowly dropping 0.2 mL of distilled water from a height of 5 mm onto the surface of the coating layer with a syringe, leaving it for 30 seconds, and then its contact angle (angle formed by the tangent line between the coating layer surface and the droplet). Was observed with a CCD camera and measured. And the same operation was repeated 5 times and the average value was used.

(13) Film thickness and thickness unevenness The thickness of the film was measured uniformly at 10 points in each 0.5 m section using an electronic micrometer in the vertical and horizontal directions, and the average thickness (unit: μm) was calculated. did. In addition, the ratio (percentage) of the difference between the maximum thickness (unit: μm) and the minimum thickness (unit: μm) to the average thickness (unit: μm) of the measured length is obtained, and the thickness unevenness (unit:%) As sought. The thickness variation in the vertical direction and the horizontal direction was taken as a measurement value.

(14) Weight average molecular weight of syndiotactic polystyrene 0.5 ml of HFIP: chloroform (1: 1) was added to 1 mg of the film and dissolved (overnight), and 9.5 ml of chloroform was added immediately before the measurement, and the membrane filter 0 The solution was filtered through 1 μm and subjected to GPC analysis. Measuring equipment and conditions are as follows.
GPC: HLC-8020 Tosoh detector: UV-8010 Tosoh column: TSK-gelGMHHR · M × 2 Tosoh mobile phase: HPLC chloroform flow rate: 1.0 ml / min
Column temperature: 40 ° C
Detector: UV (254 nm)
Injection volume: 200 μl
Sample for calibration curve: Polystyrene (EasiCal “PS-1” manufactured by Polymer Laboratories)

[Reference Example 1] (Adjustment of coating liquid 1)
As the adjustment of the coating liquid 1, the following release formation, surfactant and cross-linking agent were dispersed in water so that the weight of the solid component was 5% by mass in the weight ratio shown in Table 1, and the emulsion aqueous solution was prepared. Created.
Mold release component: Polyethylene wax (trade name: U3, manufactured by Takamatsu Yushi Co., Ltd., an emulsion of polyethylene wax, and the amount of polyethylene wax in the emulsion is described to be the content of the mold release component in Table 1. .)
Surfactant: Polyoxyalkylene alkyl ether (product name L950, manufactured by Lion Corporation)
・ Crosslinking agent: Zirconyl ammonium carbonate

[Reference Examples 2 to 4] (Adjustment of coating liquids 2 to 4)
As shown in Table 1, the same operation as in Reference Example 1 was repeated except that the content of polyethylene wax was changed and the binder resin a having the following composition was changed to the content shown in Table 1.
<Binder resin a>: Acrylic modified polyester / polyester component: 50 mol% terephthalic acid / 45 mol% isophthalic acid / 5 mol% 5-sodium sulfoisophthalic acid / 75 mol% ethylene glycol / 25 mol% diethylene glycol
Acrylic component: 90 mol% methyl methacrylate / 10 mol% glycidyl methacrylate
Polyester resin component / acrylic resin component repeating unit molar ratio = 3/7

[Reference Example 5] (Adjustment of coating liquid 5)
As the adjustment of the coating liquid 5, the following release formation, surfactant, and crosslinking agent were dispersed in water so that the weight of the solid component was 5% by weight to prepare an aqueous emulsion solution. In addition, about the silicone compound, after previously mixing with surfactant, it added to the coating liquid.
-Mold release component: Carboxy modified silicone (trade name X22-3701E manufactured by Shin-Etsu Chemical Co., Ltd.)
Surfactant: Polyoxyethylene (n = 8.5) lauryl ether (trade name NAROACTY N-85, manufactured by Sanyo Chemical Co., Ltd.)
・ Crosslinking agent: Oxazoline (trade name Epocros WS-300, manufactured by Nippon Shokubai Co., Ltd.)

  Coating solutions 1 to 5 in Table 1 were prepared in Reference Examples 1 to 5, respectively, and binder resin a means the acrylic-modified polyester of Reference Examples 2 to 4 above.

[Example 1]
As the thermoplastic amorphous resin Y, 67.5 parts by mass of polystyrene having a weight average molecular weight of 3.0 × 10 ⁵ and an almost complete syndiotactic structure observed by ¹³ C-NMR measurement, 2,6-dimethyl-1,4-phenylene) ether (inherent viscosity measured in chloroform is 0.32 dl / g, glass transition temperature is 210 ° C.) 30 parts by mass, and antioxidant (C1) is penta 2 parts by mass of erythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010, melting point 120 ° C., thermal decomposition temperature 335 ° C.) As the inert fine particles A, 0.4 part by mass of spherical silica particles having an average particle size of 0.3 μm, a relative standard deviation of 0.16, and a particle size ratio of 1.09 (It becomes 0.4% by mass in 100% by mass of the obtained biaxially stretched film) and the inert fine particle B has a spherical shape with an average particle size of 1.2 μm, a relative standard deviation of 0.15, and a particle size ratio of 1.10. The silicone resin particles were mixed with 0.1 part by mass (0.1% by mass in 100% by mass of the obtained biaxially stretched film) to obtain a resin composition.
The obtained resin composition was dried at 120 ° C. for 7 hours, then fed to an extruder, melted at 300 ° C., extruded from a die slit, solidified by cooling on a casting drum cooled to 50 ° C., and unstretched Created a sheet.

  This unstretched sheet is stretched 3.5 times in the longitudinal direction (machine axis direction) at 140 ° C., and then, after longitudinal stretching, a coating liquid 1 containing 5% of the components shown in Table 1 on one surface of the film (5% by mass water) (Dispersible coating liquid) is applied so that the final coating layer thickness is 40 nm, and then guided to a tenter. Then, the temperature at the preheating start portion is 95 ° C., the temperature at the preheating end portion (stretching start) The temperature of the portion was preheated while drying the coating solution for 9 seconds in a process of 1126 ° C., and then stretched 4.5 times in the transverse direction (direction perpendicular to the machine axis direction and the thickness direction). At that time, the stretched portion was divided into four equal zones, and the stretching speed in the transverse direction was set to 5000% / min. Further, the stretching temperature in the transverse direction was also divided into four equal parts, and the first stage temperature was 126 ° C. and the final stage temperature was 145 ° C. After that, it was heat-fixed at 250 ° C. for 9 seconds, and further cooled to 180 ° C., and then subjected to 2% relaxation treatment (toe-in) in the lateral direction to obtain a biaxially stretched film having a thickness of 3.0 μm and wound into a roll. It was. The properties of the obtained film are shown in Table 2.

[Examples 2 to 6 and Comparative Examples 1 and 2]
Table 2 shows the properties of the film obtained in the same manner as in Example 1 except that the conditions for film formation (stretch ratio) were changed as shown in Table 2. Film film with a high draw ratio has good heat resistance, but when the draw ratio is low, the storage elastic modulus (E ') at high temperature (150 ° C) is low, which corresponds to the heat resistance in the processing stage of capacitors. The shearing force after thermocompression bonding at a high temperature is increased, and the heat resistance is deteriorated.

[Examples 7 and 8, Comparative Examples 3 and 4]
As shown in Table 2, the procedure was the same as Example 1 except that the mixing ratio of polystyrene and thermoplastic amorphous resin Y was changed, and the stretching conditions for film formation were changed. The properties of the obtained film are shown in Table 2.
When the amount of the thermoplastic amorphous resin Y is small, the storage elastic modulus (E ′) at a high temperature (150 ° C.) is lowered, the shearing force after thermocompression bonding at a high temperature is increased, and the capacitor is processed at the stage of processing. Heat resistance deteriorated. On the other hand, if the amount of the thermoplastic amorphous resin Y is too large, the composition of the mixture becomes unstable, or the stretchability is deteriorated, making it difficult to obtain a roll film.

[ Comparative Example 5 ]
As shown in Table 2, the same procedure as in Example 2 was performed except that the thermoplastic amorphous resin Y was changed to bisphenol A type polycarbonate (Idemitsu Petrochemical Idemitsu polycarbonate A300, glass transition temperature 145 ° C.). The properties of the obtained film are shown in Table 2.

[Examples 10 and 11]
As shown in Table 2, the procedure was the same as Example 1 except that the content of the antioxidant was changed. The properties of the obtained film are shown in Table 2.

[Example 12]
Antioxidant (C1), antioxidant (C2): octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Ciba Specialty Chemicals, Inc., trade name: IRGANOX 1076, melting point 52.degree. C., thermal decomposition temperature 230.degree. C. The properties of the obtained film are shown in Table 2.

[Example 13]
Table 2 shows the properties of the obtained film in the same manner as in Example 1 except that the coating layer was not formed. Although the dielectric breakdown voltage was slightly lowered, the storage elastic modulus (E ′) at a high temperature (150 ° C.) was high, and the heat resistance was good.

[Examples 14 to 17]
Table 2 shows the properties of the obtained film in the same manner as in Example 1 except that the coating liquid was changed as shown in Table 2.

In Table 2, PPE, PC, C1, and C2 are as follows.
PPE: poly (2,6-dimethyl-1,4-phenylene) ether (inherent viscosity measured in chloroform is 0.32 dl / g, glass transition temperature is 210 ° C.)
PC: Bisphenol A type polycarbonate (Idemitsu Petrochemical Idemitsu Polycarbonate A300, glass transition temperature 145 ° C.)
C1: Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1010, melting point 120 ° C., thermal decomposition temperature 335 ° C.)
C3: Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Ciba Specialty Chemicals: trade name IRGANOX 1076, melting point 52 ° C., thermal decomposition temperature 230 ° C.)

[Create a capacitor]
Moreover, the capacitor was created as follows using the obtained highly insulating film.
First, aluminum was vacuum-deposited on one side of the highly insulating film (the surface of the coating layer) so as to have a thickness of 500 mm. At that time, deposition was performed in the form of vertical stripes consisting of repetition of an 8 mm wide vapor deposition portion and a 1 mm wide non-deposition portion. The obtained vapor-deposited film is slit at the center in the width direction of the vapor-deposited portion and the non-vapor-deposited portion, and is formed into a 4.5 mm-wide tape shape consisting of a 4-mm wide vapor-deposited portion and a 0.5-mm wide non-deposited portion A take-up reel. Next, the two reels were overlapped and wound so that the non-deposited portions were on the opposite end faces, respectively, to obtain a wound body, and then pressed at 150 ° C. and 1 MPa for 5 minutes. Metallicon was sprayed on both end faces of the wound body after pressing to form external electrodes, and lead wires were welded to the metallicon to form a wound film capacitor.

  The film capacitors using the films obtained in Examples 1 to 17 of the present invention were excellent in heat resistance and withstand voltage characteristics (dielectric breakdown voltage (BDV)), and exhibited excellent performance as capacitors.

  The highly insulating film of the present invention can be suitably used as an insulator for a capacitor. In particular, it can be suitably used as an insulator for a capacitor mounted on a hybrid car or the like and exposed to a relatively high temperature environment.

1: Sample 1
2: Sample 2
3: Hot plate 4: Paper 5: Feed block

Claims (7)

Thermoplastic amorphous resin Y comprising a biaxially stretched film whose main component is a styrene polymer having a syndiotactic structure, and having a glass transition temperature Tg by DSC of 130 ° C. or higher with respect to the mass of the biaxially stretched film Containing 5% by mass or more and 48% by mass or less of polyphenylene ether and 0.1% by mass or more and 8% by mass or less of an antioxidant, and a plane orientation coefficient (ΔP) represented by the following formula (1) is −0. A highly insulating film characterized by being 027 or less.
ΔP = (Nx + Ny) / 2−Nz (1)
(Where Nx is the minimum value of the refractive index in the plane direction of the film, Ny is the refractive index in the direction perpendicular to Nx in the plane direction of the film, and Nz is the refractive index in the thickness direction of the film. Show.) The highly insulating film according to claim 1 , wherein the refractive index in the thickness direction of the film is 1.580 or more and 1.610 or less .   2. The highly insulating film according to claim 1, wherein the absolute value of the difference between the minimum value (Nx) of the refractive index in the surface direction of the film and the refractive index (Nx) in the direction orthogonal to the direction is 0.025 or less.   The highly insulating film according to claim 1, wherein the biaxially stretched film has a coating layer provided on at least one surface thereof and having a surface water contact angle of 85 ° or more and 120 ° or less.   The high coating layer according to claim 4, wherein the coating layer contains at least one selected from the group consisting of a wax component, a silicone component, and a fluorine compound in an amount of 41% by mass to 94% by mass based on the mass of the coating layer. Insulating film.   The highly insulating film according to claim 1, wherein the thickness is 0.4 μm or more and less than 6.5 μm.   The capacitor | condenser using the highly insulating film of any one of Claims 1-6.

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